Lockable articulated joint

A lockable articulated joint comprising:

• a socket member having a concave, substantially frusto-spherical socket surface, and a hole extending from the concave socket surface to the opposite side of said socket member;
• a hollow member having a substantially frusto-spherical outer surface with a radius of curvature approximating that of said socket surface, a substantially frusto-spherical inner surface approximately concentric with said outer surface, and means providing a hole extending from said inner surface to said outer surface to permit a locking fastener to extend through the hollow spherical member while allowing universal articulation between said socket and said frusto-spherical member through a limited range, said hollow member extending into and engaging said socket member;
• a locking member having a substantially frusto-sperhical outer surface engaging the inner surface of said hollow member and having a radius of curvature approximating that of the inner surface of said hollow member;
• and
• a locking fastener extending through the hole in said socket member and the hole in said hollow member, and comprising means for releasably forcing said locking member toward said socket member to clamp said hollow member therebetween in a fixed relationship to said socket member;
• the radius of curvature of the outer surface of said locking member being slightly greater than that of the inner surface of said hollow member, and at least one member of said locking member and said hollow member being resilient at the locations on its surface which engage the other of said locking and hollow members within said limited range of articulation.